Reversible circulation internal fan kiln



May 14, 1935. R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN FiledNov. 23, 1932 s sheets sheet 1 FIG. 1

INVENTOR ROLF THELE/V ATTORNEY May 14, 1935. v R. THELEN 2,001,001

v REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed Nov. 25, 1932 3Sheets-Sheet 2 FIG. 2

INVENTOR ROLF THELE/V- ATTORNEY May 14, 1935. R. THELEN 2,001,

7 REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed Nov. 25, 1952 sSheets-Sheet s INVENTOR ROLF THELE/V ATTORNEY Patented May 14, 1935nEvEnsiBLE CIRCULATION INTERNAL FAN KILN Rolf Thelen, Madison, Wis;dedicated to the free i use of the Public Application November 23, 1932,Serial No. 644,010

1 Claim. (Cl. 3446) (Granted under the act of March 3, 1883, as

, amended April 30, 1928; 370 0. G. 757) This application is made underthe act of March 3, 1883, as amended by the act of April 30, 1928, andthe invention herein described may be manufactured and used by or forthe Government, for governmental purposes, without payment to me ofanyroyalty thereon.

I hereby dedicate the invention herein 'described to the free use of thepublic,,to take effect upon the granting of a-patent to me.

My invention consists in an improvement in the design of forcedcirculation. kilns for drying and conditioning lumber and othermaterials. It consists in the adaptation offans of the disk type, orsimilar types, to the production of a unique internal circulation of theair and vapor in the kiln combined with the production and regulation ofthe heat and the humidity within the kiln. I H

. This invention is illustrated in Figures 1, 2, and 3. Figure 1represents a cross-sectional elevation of the kilntaken on line 5-! ofFigure 2 and looking in the direction of the arrows. Figure 2 representsa longitudinal sectional elevation of. the kiln taken on line 2-2 ofFigure 1 and looking in the direction of the arrows. Figure 3 representsa horizontal crossesection of the kiln taken'on line 33 of Figure l andlooking in the direction of the arrows.

The principal feature which I claim as novel and an improvement overexisting kilns isthe use and arrangement of the fans and the airdistributer. This arrangement is such that a very fast and uniformcirculation of-the air and vapor through the lumber piles may be securedand it permits the periodic reversal of the direction of the air andvapor movement by reversing the direction of rotation of the fans. Theair distributer provides a very uniform flow of air throughoutthe lengthand breadth of the kiln and eliminates the non-uniformity of drywhich isone of the commonest troubles exfeature is of special advantage ininstalling fans in existing structures. The elimination ofcomparatively. small ducts such as those used in externalblowerkilnsreduces very materially the power required to produce a-givencirculation. Thedifierences in air pressure required in the operation ofthis kiln are much smaller than those ordinarily required in kilnsemploying centrifugal blowers, and the disk fans operate veryefficiently at these low pressures. Measurements recently made vindicatethat the static pressures necessary for the successful operation of thissystem are materially less than-loneeighth of an inch of water pressure.It is possible, therefore, by the use of thisinvention to produce a verylarge and uniform circulation of the air and vapor within the kiln witha very small expenditure of power.

While it is obvious that there are many possible ways in which the useof internal fans can be adapted to dry kilns of different types, thisinvention is limited to kilns in which the lumber is flat piled and inwhich the circulation of the air and vapor throughout the lumber pilesis in a substantially horizontal direction from edge to edge of thepiles.

Any well-known means of heating the air and vapor in the kiln may beused in conjunction with this invention. When steam pipes are used theymay be most conveniently arranged above the lumber piles at the sides ofthe kiln. Any convenient form and arrangement of heaters maybe used. Thetemperature may be con:- trolled by hand or by any suitable automaticmeans. i

While the drawings show and-the specification describes specific meansfor heating the air and vapor in the kiln and for regulating thehumidity of the kiln atmosphere, this invention is not limitedspecifically to the arrangements -described, but may make use of anyother wellknown and suitable means for accomplishing the same purposes.The humidity may be controlled by hand or by any suitable automaticmeans.

Referring to Figures 1, 2, and 3, which are correspondingly lettered: AAare the motors which furnish the power to drive the fans. BB are thefans producing the circulation. Straight-bladed disk fans arepreferable. Any

type of fan, however, in which the reversalof the direction of rotationof the fan produces a reversal in the direction of the flow of the aircurrent passing through the fan can be used. C0 are the shafts uponwhich the fans are mounted. Provision is made to take careof theexpansion and contraction of these shafts with changes in thetemperature in the kiln by means of a suitable flexible coupling" be:tween each motor and the fan. DD are inlet dampers used to regulate andcontrol the amount of air entering the kiln from the outside. EE are theheating coils. These may be of any convenient type and arrangement. F isthe steam jet pipe used to increase the humidity of the atmosphere inthe kiln. Suitable openings areprovided in this pipe to permit theescape of steam throughout the length of the kiln. The precise locationof this steam jet pipe is not of prime importance. Various other commonand well-known arrangements may be used. G is the support for the lumberpiles. HH are the lumber piles. II are bearings for the shafts CC. J isa hinged joint in the lower part L of the air distributor. KK are theside walls of the kiln. L is the lower part of the air distributor. M isthe upper part of the air distributor. N is the central part of the airdistributor. N is a support on the upper part of the air distributor andsupports and maintains the bearing I and air distributor assembly. Thesethree parts compose the air distributor. 00 are air outlet dampers forcontrolling the amount of air being exhausted from the kiln. P is a kilndoor. Q is the kiln roof. RR are flexible couplings between the motorsand the fans. SS are switches for controlling the speed and direction ofthe rotation of the motor armatures and fans. While the drawings showand the specification describes single speed electric motors, variablespeed or multi-speed motors, or any other suitable driving means may beused. TT are air inlet flues in which the dampers DD are fitted. UU areair outlet flues in which the dampers 00 are fitted. V is the floor ofthe kiln. WW are the side air passages between the lumber piles and theside walls of the kiln. XX are the end walls of the kiln. YY are memberssupporting the air distributor assembly. ZZ are the stickers between thelayers of lumber.

While the air distributor and the substantially horizontal arrangementof the fans are essential parts of my invention, considerable latitude,particularly in the design of the air distributor, is permitted. The airdistributor illustrated and described has been for the sake ofconvenience and accessibility divided into three parts, each of saidparts running continuously from end to end of the kiln. The upper part Mof the air distributor is a solid sheet of suitable material curved insuch manner as to facilitate the fiow of the air and vapor. The centralpart N of the air distributor is a substantially horizontal sheet ofsuitable material provided with circular openings into which the fancasings are fitted. The lower part L of the air distributor is composed,for the sake of convenience, of two suitable curved continuous sheets ofsuitable material connected together with a continuous hinged joint J.This joint permits the substantially horizontal portion of the lowerpart L of the air distributor to be dropped down for convenience ininspecting the fans. The air distributor is in the nature of a septumdividing the left half of the kiln from the right half-Figure l--andguides the flow of the air and vapor in the desired direction.

The operation of the kiln is briefly as follows:

The lumber is piled in the kiln, care being taken to provide side airpassages WW of suitable width between the lumber piles and the sidewalls of the kiln. The door and all of the dampers are closed. Steam isturned into the heating coils and into the steam jet pipe. Suitableregulating devices are provided to control and regulate the supply ofsteam to the heating coils and the supply of steam to the steam jetpipe. If it be found impossible to reduce the humidity within the kilnto the desired point with the steam jet pipe closed, the dampers DD and00 are opened to allow fresh air to enter and moist air to escape. Thesedampers should be adjusted so that a humidity somewhat below thatdesired will be secured. The steam jet pipe may then supply a sufficientamount of steam to bring the humidity up to the desired point. Referringto Figure 1; if the direction of rotation of the fans BB is such thatthe air and vapor pass downward through said fans the lower part L ofthe air distributor will deflect said air and vapor to the right andupward. Thence the path of the movement of said air and vapor isdownward through the right-hand heating coils E into the right-hand sideair passage W, thence horizontally through the lumber piles l-II-I intothe left-hand side air passage W, upward through the left-hand heatingcoils E, past the steam jet pipe F, and thence back to the fans BB,repeating the cycle continuously. When the direction or" the rotation ofthe fans BB is reversed the direction of the circulation of the air andvapor is likewise reversed. The location and arrangement of the variousparts eliminate the necessity for air diifusers and especiallyconstructed plenum chambers. The heating coils EE act effectively as airdifiusers and the comparatively large spaces above said heating coilsact in the capacity of plenum and vacuum chambers, materially assistingin the uniform distribution of the air and vapor lengthwise of the kiln.

It is well understood that when the circulation of the air and vapor ina kiln is continuously in one direction, that portion of the lumberpiles at which the air and vapor enter will dry more rapidly than theopposite side since the air in its passage through the lumber pilespicks up moisture and thus reduces its drying capacity. The reversal ofthe direction of the air circulation overcomes this defect since thatedge of each lumber pile which was the entering air edge before reversalbecomes the leaving air edge after reversal. These portions of thelumber piles which dried fastest before reversal dry most slowly afterreversal. The reversal of the circulation will in practice be doneperiodically every two or three days or oftener, the exact period beingdetermined by the condition of the lumber in the kiln.

Having fully described the principles of this invention and a manner inwhich they can be embodied in a dry kiln, I claim as original:

In a dry kiln adapted to receive a single row of fiat piled stacks oflumber, comprising a plurality of horizontal fans centrally locatedabove the lumber; heating coils located at the side walls above thelumber; an air distributor centrally located above the lumber, extendingthe full length of the dry kiln and consisting of a substantiallyhorizontal central part, provided with means for supporting said fans,and extending from a point in proximity to said heating coils on oneside to a point in proximity to said heating coils on the other side ofthe kiln; a curved upper part extending from one edge of said centralpart to the dry kiln ceiling, and a curved, hinged, lower part,extending from the other edge of the central part substantiallytransversely across the dry kiln to a point in proximity to said coilsopposite said other edge of said central part, and reversible drivingmeans for said fans.

ROLF THELEN.

